Question

A block of mass $10kg$ is pulled at constant speed on a rough horizontal surface by a force of $19.6N$. The coefficient of friction is

• A. $0.1$
• B. $0.2$
• C. $0.3$
• D. $0.4$

Answer 1

The correct option is B $0.2$

From the given data we can say that the acceleration of the block is zero since it is moving at constant speed.
Given, mass of the block $m=10kg$ and the applied external force $F=19.6N$
Let $f$ be the friction force acting on the block
$\Rightarrow F-f=ma$
$\Rightarrow F-f=0\Rightarrow F=f=\mu mg$
$\Rightarrow 19.6=\mu \left(10g\right)$
or, $\mu =\frac{19.6}{10\times 9.8}=0.2$